Characterization and stabilization of enzyme biosensors

Synthesis of novel amperometric urea-sensor using hybrid synthesized NiO-NPs/GO modified GCE in aqueous solution of cetrimonium bromide

In this study NiO nanostructures were synthesized via combinational synthetic method (ultrasound-assisted biosynthesis) and immobilized on the glassy carbon electrode (GCE) as a highly sensitive and selective enzyme-less sensor for urea detection. NiO-NPs were fully characterized using SEM, EDX, XRD, BET, TGA, FT-IR, UV-vis and Raman methods which revealed the formation of NiO nanostructures in the form of cotton like porous material and crystalline in nature with the average size of 3.8 nm. GCE was modified with NiO-NPs in aqueous solution of cetrimonium bromide(CTAB). Highly adhesive NiO/CTAB/GO nanocomposite membrane has been formed on GCE by immersing NiO/CTAB modified GCE in GO suspension. CTAB has a major role in the production and immobilization of the nanocomposites on the GCE surface and the binding NiO nanoparticles on GO plates. In addition, CTAB/GO composition made a highly adhesive surface on the GCE. The resulting NiO/CTAB/GO/GCE contains potently sensitive to urea in aqueous environments. The response of as developed amperometric sensor was linear in the range of 100-1200 µM urea with R² value of 0.991 and limit of detection (LOD), 8 µM. The sensor responded negligibly to various interfering species like glucose, uric acid and ascorbic acid. This sensor was applied successfully for determining urea in real water samples such as mineral water, tap water and river water with acceptable recovery.

Facile synthesis of manganite nanowires: phase transitions and their electrocatalysis performance

In this paper, ultrathin (about 2.5 nm) manganite (MnOOH) nanowires were synthesized by a simple wet chemical method at ambient temperature. Temperature-dependent phase transition patterns of the prepared nanowires under different atmospheres were systematically studied with thermogravimetric and differential thermal analysis (TG/DTA). Based on the critical temperatures demonstrated by the phase transition pattern, manganese oxides, such as Mn2O3 and Mn3O4, have been obtained conveniently through calcination. Scanning electron microscope (SEM), transmission electron microscope (TEM) and x-ray diffraction results confirm that the annealed nanowires can both retain their original 1D morphology and show good crystallinity. The electrocatalytic performance of the as-prepared manganese oxides was also explored, which showed good response to the reduction of H2O2 in alkaline media. Among the three manganese oxides, the MnOOH nanowires exhibited the most prominent electrocatalytic efficiency and stability, which provides a good candidate for modern industrial catalysis applications.